Robot systems for coating, and specifically paint spraying, are now well established particularly for production line use in applications in which relatively flat, easy to access surfaces are presented to the spray gun such as parts moving along an assembly line. The robot moves and coordinated gun operations in such systems are relatively simple and have been developed to a high degree.
A need exists, however, for a robot spray gun system which is adapted to apply coatings to large, non-regular surfaces in a very precise and controlled pattern. One such application is the aerospace industry where large, irregularly shaped structures must be coated. An airplane is a good example of such an application. Today's aircraft standards are exceedingly high as compared to only a few years ago and present robot systems are either too slow, not sufficiently accurate, cannot access all surfaces, or not cost efficient, and usually a combination of some or all of the foregoing. Military aircraft, for example, may require up to 50 very thin coating applications on some exposed surfaces, and the time required to meet this standard with present equipment is unacceptably long and, often, of insufficient quality. As will be appreciated such structures as airplanes have flat surfaces, numerous junctions, but mostly curvilinear contours, all of which dictate that the robot must operate with a very high degree of precision.
Accordingly, objectives of this invention are to provide a robot with the ability to follow complex trajectories that require widely varying speeds and high acceleration, an enormous useful work envelope, low maintenance, particularly as regards malfunction of hydraulic and electrical lines and components which, because of their generally exposed conditions, are subject to damage and consequent malfunction, and counter balanced coating application; i.e., a coating applicator which has the capacity of near instantaneous response to motion commands due in part to the absence of gravitational torque in the system.
In a specific embodiment of the invention a fully integrated robot system is provided which is capable of painting an entire aircraft The system includes a transporter sub-system which carries a robot sub-system. The transporter is provided with three degrees of freedom, namely, a vertical; i.e., a Z axis movement for the entire system, a first horizontal rotational movement provided by a first boom which rotates about the Z axis, and a second horizontal rotational movement provided by a second boom or arm which rotates about a vertical axis carried by the first boom at the point of attachment of the first boom to the second boom. The robot sub-system has six degrees of freedom, said sub-system being mounted at the end of the second boom or arm of the transporter. Preferably the robot sub-system has a first degree of freedom about a vertical axis, a second degree of freedom about a first horizontal axis, a third degree of freedom about a second horizontal axis which is parallel to the first horizontal axis, and a wrist mechanism capable of movements about roll, pitch, and yaw axis.
Further attributes of such a system are that (i) the work envelope is dramatically increased over prior systems, (ii) oil connections are made through integrated multi-port swivel fittings, (iii) all leak paths drain back to tank thus making the system virtually leak free, (iv) the hydraulic connections are totally enclosed within the robot arm and base and therefore protected to the maximum extent possible which results in low maintenance and a smooth, clean look, (v) overhanging structures which currently are common are not present, (vi) reliability is increased, and (vii) the work envelope has redundant access to achieve 100% attainability to all surfaces to be coated.